1. Field of the Invention
This invention relates to a fiber optic coupling arrangement, and in particular to an arrangement for integrating parallelepiped-shaped (hereinafter referred to as "rectangular") fiber optic connectors or ferrules into a mating pair of cylindrical connectors having environmental sealing, anti-vibration, and coupling features in common with cylindrical electrical connectors.
2. Description of Related Art
Copending U.S. patent application Ser. No. 09/149,568, filed Sep. 9, 1998, discloses an arrangement for integrating rectangular fiber optic connectors or ferrules into a standard cylindrical multiple contact connector system of the type heretofore normally used to house electrical contacts. In order to facilitate integration of the rectangular fiber optic connectors or ferrules into the standard cylindrical multiple contact connector system, the fiber optic connectors or ferrules are captured between halves of respective cylindrical contact housings. The cylindrical contact housings are configured such that they can take the place of the electrical contacts in the standard cylindrical multiple contact connector, permitting the same basic connector design to be used for both electrical and fiber optic connections.
The present invention also utilizes cylindrical fiber optic contact housings of the type disclosed in U.S. patent application Ser. No. 09/149,568, but applies them to a more robust connector arrangement having enhanced environmental and shock or vibration protection features that permit the connector to be used under adverse conditions, such as in military or aerospace applications. In particular, whereas the connector described in the copending application utilizes a standard connector shell and inserts, the present invention modifies the shell and inserts in order to provide enhanced alignment functions for the fiber optic ferrules or connectors, and to better accommodate environmental sealing and shock or vibration resistance features, without sacrificing the advantages of simplicity and ease-of-use offered by the connectors described in the copending application.
As in the copending application, the present invention is suitable for use with the rectangular fiber optic connector structure known as the "Mechanical Transfer" (MT) connector or ferrule, which is essentially a housing that encapsulates the ends of a plurality of fibers and thus aids in aligning the fibers so that the ends of the fibers can be mechanically joined together to establish a connection between the respective groups of fibers housed or encapsulated by the mating ferrules.
In general, in order to establish a connection between two groups of optical fibers, most fiber optic connector systems require, in addition to a ferrule structure for holding the fibers, some sort of external shell and/or coupling arrangement that aligns the MT connectors and allows them to be joined together. While some of the known coupling arrangements are widely used, however, the known fiber optic coupling arrangements are either difficult to use, relatively complex, or lack robustness in comparison with electrical connectors. Such a trade-off between ease-of-use, complexity, and robustness has heretofore been assumed to be essentially inherent in fiber optic connector designs because of the precise alignment required of fiber optic connections, resulting in a tolerance for cost and complexity among fiber optic users that would not be acceptable in the case of electrical connectors.
In the case of MT and other rectangular fiber optic connector systems, the rectangular shape of conventional coupler designs, which follows from the shape of the ferrule, compounds the above-noted disadvantages of fiber optic connectors in general by making environmental sealing difficult, and precluding use of simply coupling nut arrangements which simply require threading of a coupling nut on one connector onto the mating connector.
One such conventional connector system, the MTP fiber optic connection system, requires both mating pairs of MT connectors, which are housed within two identical spring loaded connector sections, and a separate coupling device into which the spring-loaded sections must be inserted. The need for a separate coupling device increases the time required to establish a connection and makes it difficult to include environmental protection or vibration resistance features and, moreover, once the two rectangular coupling members are joined together via the third coupling device, there is no way to decouple the MT connectors in order to replace or repair them.
On the other hand, the alternative MT ferrule connector system described in U.S. Pat. No. 5,619,604 eliminates the need for a separate coupling device, but requires that the MT connectors be housed in relatively complex and fragile five-piece shells, including both a guide pin and aperture arrangement and also a guide prong and tongue arrangement, to provide necessary alignment between mating ferrules.
Thus, present fiber optic coupling arrangements that employ rectangular fiber optic connectors are either inconvenient in that they require a separate coupling member, or are relatively complex. In addition, most such coupling arrangements are not suitable for use in non-office environments, lacking sealing and shock or vibration protection features that would only add to their complexity or make them less convenient to use.
The present invention, in contrast, provides a connector system for MT and other rectangular or parallelepiped-shaped connectors with complete environmental sealing and shock or vibration protection, and that can be coupled in a simple manner under adverse conditions. Essentially, the present invention seeks to apply principles which have been learned over the course of many years through experience with electrical connectors, as represented in part by the current military specifications, in order to place fiber optic connectors on a par with electrical connectors in terms of ease-of-use and robustness, and thereby eliminate the dichotomy between electrical and fiber optic connectors that has existed since fiber optic connectors first began to be commercialized. Furthermore, by merging fiber optic and electrical connector designs, the present invention has the additional advantage of enabling use of standard parts such as o-rings and gaskets, as well as standard assembly and installation procedures.
In addition to the above-mentioned MTP system and the arrangement disclosed in U.S. Pat. No. 5,619,604, background for the present invention includes various proposed arrangements involving integration of rectangular fiber optic connectors into specially designed cylindrical connector housings arranged to collectively accommodate multiple rectangular fiber optic connectors, rather than to accommodate individual cylindrical contact shells in which are captured the fiber optic connectors, and which therefore lack the advantages of simplicity and standardization provided by the present invention. Examples of such arrangements are described in U.S. Pat. Nos. 4,142,776 and 5,689,598. Other references showing cylindrical fiber optic coupler configurations, but which do not utilize rectangular MT connectors or ferrules, include U.S. Pat. Nos. 5,715,342, 5,283,848, 5,000,536, 4,174,882, and 4,140,367.
Because it is impossible to describe in detail every possible connector configuration in which the present invention could be used, the detailed description of the preferred embodiment presented below is particularly directed to the size 9 cylindrical connector referred to in U.S. Department of Defense specifications as the MIL-C-38999 Series III connector. This connector is particularly advantageous from the standpoints of robustness, ease-of-use, installation, and servicing under difficult conditions. It should nevertheless be appreciated that the goals of robustness and ease-of-use, installation, and servicing are also relevant to civilian applications such as avionics, and even to coupling arrangements intended for use in office environments, and that since none of the above-cited references discloses integration of a rectangular fiber optic connector, such as an MT connector or ferrule, into a standard cylindrical connector housing of the type conventionally used to establish electrical connections, those skilled in the art should appreciate that the invention is intended to generally cover any arrangement for integrating rectangular fiber optic connectors into cylindrical connectors by enclosing individual rectangular fiber optic connectors in cylindrical contact housings for insertion into cylindrical connectors, and is not to be limited to "Mil Spec" connectors, or to any particular cylindrical connector configuration.